Lactic Acid

Gentle hydroxy acid that exfoliates and hydrates skin.

Also known as: 2-hydroxypropanoic acid, milk acid, INCI: Lactic Acid

What it is

Lactic acid is an alpha-hydroxy acid (AHA) naturally derived from milk fermentation or synthesized chemically. It's a small-molecule organic acid that dissolves the bonds between dead skin cells on the skin's surface.

What it does

Lactic acid exfoliates by breaking down desmosomes (the "glue" holding dead skin cells together), revealing fresher skin beneath. Unlike stronger AHAs, it also has humectant properties—it draws moisture into the skin—making it gentler and less likely to cause irritation. It can improve skin texture, reduce fine lines, and brighten dull complexions.

The evidence

Strong clinical evidence supports lactic acid's efficacy for gentle exfoliation and hydration; multiple studies confirm it reduces fine lines and improves skin texture at 5–12% concentrations. Evidence is particularly robust for its dual exfoliating and moisturizing action compared to other AHAs.

Best for

Sensitive, dry, and reactive skin types; those seeking gentle exfoliation without irritation; mature skin concerned with fine lines and texture.

Pairs well with

Niacinamide, hyaluronic acid, ceramides, peptides, and gentle hydrating serums. Works well in layered routines with retinol (on alternate nights) or vitamin C.

Use cautiously with

Avoid combining with other strong AHAs or BHAs on the same day; use cautiously with vitamin A derivatives at high concentrations to prevent over-exfoliation. Not ideal with benzoyl peroxide (pH incompatibility).

Cautions

May cause mild irritation, redness, or sun sensitivity at first; always use SPF 30+ during the day. Avoid during pregnancy unless approved by a healthcare provider. Discontinue if severe irritation occurs. Start at low concentrations (5–8%) and increase gradually.